LTT 9779 b
LTT 9779 b is a Neptune-like planet orbiting the G7 V star LTT 9779 in the constellation Sculptor. It lies about 262 light-years from Earth and was discovered in 2020 using the transit method.
How Big Is LTT 9779 b?
LTT 9779 b has a radius of 4.72 times that of Earth. Its mass is 29.3 times that of Earth, giving it a density of 1.54 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is LTT 9779 b in the Habitable Zone?
LTT 9779 b orbits inside the inner edge of the habitable zone of LTT 9779. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of LTT 9779: 0.631–1.502 AU (conservative: 0.799–1.424 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on LTT 9779 b
The equilibrium temperature of LTT 9779 b is about 1,978 K (1,705 °C) — hot enough to melt many metals. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C.
Orbit and Year Length
A year on LTT 9779 b — one full orbit around LTT 9779 — lasts just 19.0 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.017 AU — closer to its star than Mercury is to the Sun.
How Was LTT 9779 b Discovered?
LTT 9779 b was discovered in 2020 using the transit method, with observations from Transiting Exoplanet Survey Satellite (TESS).
The transit method watches a star for the tiny, regular dip in brightness that occurs when a planet crosses in front of it. The depth and timing of these dips reveal the planet's size and orbital period.
How Far Away Is LTT 9779 b?
LTT 9779 b is 262.4 light-years (80.4 parsecs) from Earth. Light arriving here tonight left the planet around the year 1764. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 4,618,240 years to make the journey.
Earth Similarity Index
The Earth Similarity Index (ESI) scores how physically similar a planet is to Earth, from 0 to 1, based on radius, density, escape velocity and surface temperature. LTT 9779 b scores 0.16, ranking #4,167 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: LTT 9779
LTT 9779
- Spectral type
- G7 V
- Surface temperature
- 5,443 K (Sun: 5,772 K)
- Mass
- 1.02 M☉
- Radius
- 0.95 R☉
- Luminosity
- 0.6800 L☉
- Age
- 2.0 billion years (Sun: 4.6)
Planetary System
LTT 9779 b is the only planet known to orbit LTT 9779 so far.
LTT 9779 b — Complete Data
| Radius | 4.720 Earth radii (0.421 Jupiter radii) |
|---|---|
| Mass | 29.32 Earth masses (0.092 Jupiter masses) |
| Density | 1.54 g/cm³ (Earth: 5.51) |
| Orbital period | 0.79 days |
| Orbital distance | 0.017 AU |
| Equilibrium temperature | 1,978 K (1,705 °C) |
| Earth Similarity Index | 0.16 |
| Distance from Earth | 262.4 light-years (80.4 parsecs) |
| Constellation | Sculptor |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2020 |
Data: NASA Exoplanet Archive, last updated 2020-09-17. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About LTT 9779 b
Is LTT 9779 b habitable?
No — LTT 9779 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is LTT 9779 b?
LTT 9779 b is about 262 light-years from Earth in the constellation Sculptor. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 4,618,240 years to get there.
How big is LTT 9779 b compared to Earth?
LTT 9779 b has 4.72 times the radius of Earth and about 29.3 times its mass.
How long is a year on LTT 9779 b?
One orbit around LTT 9779 takes 0.8 Earth days — short enough that 461 of its years would fit into one Earth year.
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